1. Field of the Invention
This invention relates to a recording medium to be used preferably for ink jet recording and a recording method by use thereof, particularly to a recording medium excellent in ink receptivity, sharpness, storability, water resistance, and surface gloss of the recorded image, etc., and a recording method by use thereof.
2. Related Background Art
Ink jet recording performs recording by generating small droplets of ink by employing various ink (recording liquid) ejecting systems, such as an electrostatic attraction system, the system of giving mechanical vibration or displacement to ink by use of a piezoelectric element, the system in which the pressure formed when ink is bubbled by heating is utilized, then permitting them to fly and attaching a part or whole thereof onto a recording medium such as paper. This method is now attracting attention as a recording method which generates less noise and is capable of performing high-speed printing and multi-color printing.
As inks for ink jet recording, there have been used those composed mainly of water and a hydrophilic solvent, primarily for the reasons of safety and recording characteristics, and in most cases, a polyhydric alcohol is added for prevention of clogging of nozzles and improvement of ejection stability.
As the recording medium to be used for the ink jet recording method, there have been employed recording media comprising a porous ink-receiving layer provided on a conventional paper or a substrate known as the ink jet recording paper.
However, as ink jet recording is improved in performance, such as speed or multi-coloration, and is popularized, the recording medium also is required to have a higher level of characteristics.
More specifically, it is required that ink should be absorbed as rapidly as possible, and that the spread of ink droplets should be adequate.
Further, for carrying out color jet recording by use of color inks, a recording medium is required which is particularly excellent in color forming property and sharpness and can give high coloration.
Further, the recorded image by ink jet recording is required to be excellent in storability, durability and water resistance.
While the recorded images obtained by the ink jet recording method have been employed exclusively for surface image observation, recording media suited for uses other than for surface image observation are being demanded because of the improvement in performances or the wide popularization of ink jet recording.
Uses of the recording medium other than for surface image observation may include those in which recorded images are projected onto a screen, etc. by means of an optical instrument such as a slide or an OHP (an overhead projector), etc., color resolution plates for preparation of a positive plate for color printing; CMF (a color mosaic filter), etc. to be used for color display such as liquid crystal, etc.
When the recording medium is to be used for surface image observation, the diffused light of the recorded image is observed, while the transmitted light through the recorded images becomes a problem in the recording medium in the uses other than surface observation. Accordingly, light transmissivity, particularly excellent linear transmittance is required in addition to the general requisite performances of the recording medium for ink jet recording.
However, prior to the present invention, no recording medium satisfying all of these requisite performances has yet been known.
Also, most of the recording media for observation of the surface image of the prior art have used a system in which a porous ink-receiving layer is provided on the surface to fix the recording agent by receiving ink in the porous void, and therefore, the surface of the recording medium has no gloss based on the fact that it is porous.
On the other hand, when the surface of the ink receiving layer is non-porous, volatile components such as polyhydric alcohol, etc., in the ink will remain on the surface of the recording medium after recording. Thus it will take a long time for drying and fixing of the ink, whereby there are involved the drawbacks such that clothing may be soiled by contact with a recorded image or that the recorded image may be damaged.
However, as described above, there is a strong demand for a recording medium having light transmissivity and a recording medium having gloss on the surface. In the case of recording media of such embodiments, it is essential that the surface of the recording medium be non-porous. For such demands, in order to enhance affinity for ink and ink receptivity, it has been the practice in the prior art to use a recording medium comprising a non-porous ink-receiving layer formed by use of a water-soluble polymer.
For example, U.S. Pat. No. 4,503,111 (Tektronics) proposes a recording medium having a non-porous ink-receiving layer formed by using primarily a polyvinylpyrrolidone.
However, such a recording medium has the problems such that the recorded image is low in light fastness, or that due to strong stickiness of the surface of the ink receiving layer after receiving the ink, blocking is liable to occur when the printed media are placed one upon another, or when a paper, etc., is superposed on the recorded surface. Thus, even in such a recording medium, when the recording medium is placed under high humidity, attachment of water droplets, etc., on the surface of the recording medium will cause the surface of the ink receiving layer to have stickiness, whereby troubles may be caused such as mutual blocking between recording media or sticking of the recording medium to the conveying system of a printer, etc. In the recording medium after recording, there is also the problem that the recorded image may be damaged by migration or flowing-out, etc., of the dye at the printed portion.